Why a laboratory at all
A diamond carries no visible quality label. Weight can be weighed, but colour, clarity and cut quality are gradings made by trained staff under standardised conditions. So that buyer and seller talk about the same thing, it has become standard for an independent laboratory to describe the stone – independent meaning: the laboratory sells no diamonds and has no stake in the result.
GIA – Gemological Institute of America
Founded in 1931 in Los Angeles, today headquartered in Carlsbad, California, with laboratories in New York, Antwerp, Mumbai, Hong Kong, Tokyo, Dubai and elsewhere. In the 1950s GIA developed the 4C system – the colour scale from D to Z and the clarity scale from Flawless to Included – that all major laboratories use today. It is organised as a non-profit and regarded internationally as the reference.
Particulars: a cut grade is assigned to round brilliants only. Most stones receive a laser inscription with the report number. Verification: GIA Report Check.
IGI – International Gemological Institute
Founded in 1975 in Antwerp, today with laboratories in many trading centres, among them Antwerp, Dubai, Mumbai, Surat, Hong Kong, Bangkok, New York and Los Angeles. IGI grades natural and laboratory-grown diamonds as well as jewellery and is among the largest laboratories by volume. Reports state shape, weight, measurements, colour, clarity, cut assessment, polish, symmetry and fluorescence; laser inscriptions are customary. Verification: IGI Verify.
HRD Antwerp
HRD stands for Hoge Raad voor Diamant, the Diamond High Council, founded in 1973 in Antwerp as an institution of the Belgian diamond sector. The HRD Antwerp laboratory has graded diamonds since 1976 and is especially widespread in Europe. It uses GIA's scales, partly with its own terms: "Loupe Clean" (LC) corresponds to Internally Flawless; cut assessments are given separately for proportions, polish and symmetry. Verification: my.hrdantwerp.com.
The scales at a glance
| Criterion | GIA | IGI | HRD Antwerp |
|---|---|---|---|
| Colour | D–Z | D–Z | D–Z |
| Clarity | FL, IF, VVS1–I3 | FL, IF, VVS1–I3 | LC, VVS1–I3 (P1–P3 on older reports) |
| Cut grade | round brilliant only: Excellent–Poor | Ideal/Excellent–Poor | proportions: Excellent–Fair |
| Polish / symmetry | Excellent–Poor | Excellent–Poor | Excellent–Fair |
| Fluorescence | None–Very Strong | None–Very Strong | Nil–Very Strong |
| Online verification | yes | yes | yes |
| Laser inscription | mostly | customary | on request |
Which laboratory is "the best"?
The question is often asked in the trade and cannot be answered as such. All three laboratories work with the same scales; differences in the grading of individual stones occur between laboratories and also within the same laboratory, because colour and clarity are gradings made by people. What you can check: that the report is genuine (online verification), that it belongs to the stone (measurements, inscription, plotting diagram) and that it is current (date).
A report from one of these three laboratories is recognised in international trade. Reports from unknown or dealer-owned "laboratories" are not.
What every report states
Regardless of the laboratory you find the same core entries: report number and date; shape and cutting style; weight in carats to two decimal places; measurements in millimetres (length × width × depth, for round brilliants smallest and largest diameter); colour; clarity; cut assessment, polish and symmetry; fluorescence; on full reports a plotting diagram and a proportion diagram with table, depth, crown and pavilion angles, girdle thickness and culet; plus comments, for instance on a laser inscription or on characteristics the diagram cannot show. A statement "natural diamond" or a check for treatments is part of the report at all three laboratories – a stone with evidence of treatment (HPHT, irradiation, fracture filling) is marked as such.
Older reports and regrading
A report describes the stone on the date of issue. Diamonds do not change, but scales and methods have been refined: the GIA cut grade for round brilliants has existed since 2006; older reports state proportions only. A stone can be resubmitted at any time; the new report then replaces the old one, and the old number is recorded as superseded in the database. Anyone buying a stone with a very old report can consider regrading – it costs a fee and some time but brings current entries and an inscription.
The same laboratory for comparisons
Anyone comparing two stones should put reports from the same laboratory side by side. The scales are the same across laboratories, but the grading of the same stone can differ by one step, because colour and clarity are visual judgements. A comparison of "G at GIA" against "F at another laboratory" is therefore less meaningful than two GIA reports side by side.
Which reports you find in our shop
We list stones with reports from GIA, IGI and HRD Antwerp. On every stone's page the laboratory appears next to the report number, and the number is linked to that laboratory's verification service. Which laboratories are represented in the current stock is shown by the "Laboratory" filter in the configurator.